Hydraulic brake mechanism



FARINA HYDRAULIC BRAKE MECHANISM Aug. 1%, 1938..

Filed Feb. 26, 1937 Patented Aug. 1.6, 1938 PATENT OFFICE 7 HYDRAULICBRAKE MECHANISM Giovanni Farina, Turin, Italy Application February 26,1931, Serial No. 128,009 In Italy December 31, 1936 4 Claims.

the return of the liquid, said bores being of course covered by thepiston at the beginning of the pressure stroke. In heavy duty vehicles,in which the brake is'mechanically actuated for instance by means ofpressure air, the pressure stroke 0 starts violently and a very highpressure is suddenly created on the piston face which strongly pressesthe edge of the rubber cup of the piston against the cylinder wall andconsequently produces a rapid wear of said cup as a result of thedeformations it undergoes as it passes over the circular bores which arealways of substantial width.

It is an object of this invention of reducing or eliminating thisdrawback.

With this and incident objects in view. the invention comprises somenovel constructions of master cylinders for hydraulic brake mechanismsregarding the shape of the bores for the passage of the liquid.

The accompanying drawing shows by way of example two constructionsaccording to this invention.

Figure 1-.is a longitudinal section of a master cylinder made of onepiece.

Figure 2 is a sectional view thereof on a larger scale on line 11-11 0!Fig. 1.

Figure' 31s a longitudinal section on an enlarged scale of a dividedmaster cylinder construction having numerous longitudinallydirectedshort slots.

Referring to Figures 1 and 2, the. master cylinder I with the piston 2is provided with the ordinary rubber packing 3. Near the piston anddirectly in front of same when in its inoperative position a slot 6 iscut in the cylinder wall for establishing communication between thecylindri cal chamber I and the liquid reservoir through the connection4. The cylinder l is slightlyenlarged at 5 opposite this slot and insidethe enlargement an annular chamber 5' is formed which opens into theconnection 4. Further'slots 6 are cut .in the wall between the annularchamber 5' and the cylindrical chamber I; all

the slots 6 are less than millimeters in width and in number such as togive a total open area suflicient for the flow of the liquid. Instead oftwo or more slots one slot measuring 360, that v is a circular slot maybe provided. The slots or slot are obtained by means of a very thinmilling cutter F (Figure 2) smaller in diameter than the (Cl. Gil-54.6)

cylindrical chamber 1' into which it is introduced.

The same result may be obtained by cutting numerous short longitudinalslots. This may be obtained in a practicable manner by cutting notchesin the edge of a tube by means of a very thin milling cutter andclamping this edge against the edge of a tubular member having the sameinner diameter. Figure 3 has been obtained by this method. In thisconstruction the cylinder i is formed in the region of the passages ofthe liquid with a shoulder 1a against which is tightly pressed the edgeor a tube 1 having the same inner diameter (obtained by reaming afterassembly) as the chamber 1. The tube is tightly screwed to the openingof the cylinder I, both members being screw-threaded at III at theirrear ends and provided with a packing ring ll. Before assembly verynarrow notches 9 are cut in the edge of the tube I, whichin combinationwith the shoulder 1a. form slots opening into the annular channel 8obtained at the connection 4 by reducing the outer diameter of the tube1.

The constructions shown in Figures 1 and 3 are equivalent, for bothemploy very narrow slots, smallerin width than millimeters for thepassage of the liquid; in the construction shown in Figure 1 furtherslots might be cut beside the slots 6 to slightly extend the zone of thepassages in a longitudinal direction as in the construction shown inFigure 3. g

This slight extension of the zone of the passages in a longitudinaldirection maybe advantageous when rubber cups 3 are employ which easilyelongate in use.

I wish it to be understood that I do not desire to be limited to theexact details of construction shownand described, for obviousmodifications will occur to a person skilled in the art.

What I claim is: p

1. A ram comprising a. cylinder, a piston slidable in said cylinder,flexible cup-shaped packings for said piston, said cylinder beingprovided with inlet slots having a width of the order of millimeters toprevent the edge of said cupshaped packing from bulging in said slotsunder the action of high pressure.

2. A ram, comprising a cylinder, a piston slidvable in said cylinder,flexible cup-shaped pack lugs for said piston, a conduit for supplyingfluid to said cylinder, when-the piston reaches the end of its returnstroke. a peripheral collector formed The construction shown in one slotnot exceeding millimeters in width connecting the inside of the cylinderwith said collector.

A ram as claimed in claim 2 in which a plurality of narrow slots areformed transversely of the cylinder axis.

4. A ram, comprising a cylinder formed by an external section having aninner abutment and an internal section one end of which has short radialcuts not exceeding millimeters in width and a reduced outer diameter,said internal section being fitted on the external section so as tobring said end against said abutment, an inlet conduit communicatingwith the space formed between the external section and said reduced endof the internal section and, through said cuts, with the inside oi thecylinder, 9. piston slidably mounted in said cylinder and flexiblecupshaped packings for said piston cooperating with said cuts.

GIOVANNI FARINA.

